Abstract

The writer considers the subfamily Perlinae to include the Perlidae which have the male subanal lobes little modified (not produced into sharp hooks), which have the tenth tergite cleft and the posterior angles of the cleft thickened and produced into forward-pointing processes or “genital hooks,” and which have three normal ocelli (Ricker, 1943). A systematic review of the subfamily is badly needed, but since the species are mostly Old World ones, it will probably be done by a student having good access to such material. However, the Old World species currently included in Perla, having rather large, simple genital hooks, seem sufficiently different from all American species that the latter should not be included in the type genus. Another fairly distinct group is Neophasganophora Lestage (Phasganophora Klapálek), which has a single species in America. There is a considerable number of species, including the five discussed in this paper, in which the genital hooks have a large callus or shield (“Schwiele”) on the inner side. Whether all such species should be included in one genus is debatable; if so, the genus would include most or all of the species ascribed by Klapálek (1923) to Paragnetina, Tylopyge, Togoperla and Banksiella. Whether or not one inclusive genus of this extent should be recognized, the five American species seem to be best contained in a single genus. The genital hooks of all are rather short, not cleft at the tip, and have the callus well developed. They all have a median backward-pointing lobe on the male eighth tergite, though this is quite small in kansensis. In the female, all five species have the subgenital plate slightly to moderately produced, and bearing a small median notch or excavation. Variety appears in the presence or absence of a posterior extension of the male fifth tergite, excavated or bifid at the tip: this is present in media, immarginata and fumosa, but absent in kansensis and fattigi. The type species of Paragnetina also has such a process. At a subgeneric level a separation of the species lacking it from those which have it would probably be useful, but the matter should be left for a comprehensive revision of the group. Currently our five species are involved in an annoying confusion of specific and generic nomenclature.